Signal reproducing means



Feb. 4, 1941. w. c. WELLMANN SIGNAL REPRODUCING MEANS Filed 'March 15,199 2 Sheets-Sheet 1 im; :100-05m Malena-015m apano/7m /qmmaifm 5711;anmaim d www fw. mi m M Feb. 4, 1941. w c, WELLMANN 2,230,854

SIGNAL REPRODUCING. MEANS .FledMarCh l5, 1939 2 Sheets-Sheet 2 PatentedFeb. 4, 1941 UNITED STATES PATENT OFFICE 8 Claims.

This invention rela-.tes to signal reproducing means.

An object, among others, of my invention is to provide improvements inmeans for reproducing sound from sound recording means.

Another object is the provision of means whereby a standard radio setmay be used in conjunction with a sound projector for reproduction ofsound from sound film.

More particularly, an object, among others, of my invention has been theprovision of means whereby a sound projector for sound lm may beconnected up to a standard radio so that the radio may be used toreproduce sound recorded on sound film.

Still another obje-ct of my invention has been the provision of meansfor eliminating hum in signal reproducing means.

2 Another object has lbeen the provision oi `means for regulatingvarious tones such as high and low tones in signal reproducing means.

Another object has been to provide for preliminary heating of thefilaments of the rectifier tubes by any electrical current prior toenergizing the whole circuit, so as to make possible the operation ofthe lament circuit on direct current which provides for the reduction ofhum throughout the whole circuit, including the exciter lamp.

Another object has been to provide improvements in respect of variousfeatures of signal reproducing means.

Other objects include the production of the above means at radically lowcost and with improved eihciency.

By means of my invention, one advantage among others is that theordinary radio in a home, for example, may be used by a person desiringto project sound from a sound iilm and also to give improved soundreproduction at radically low cost.

Other objects and advantages will appear hereinafter and be brought outmore fully in the following specification, reference being had to theaccompanying drawings, wherein;

Fig. 1 is a diagrammatic View of a circuit arrangement embodying thefeatures of the invention and showing the receiver set directlyconnected to detect the audio waves;

2 is a fragmentary view of an alternate 'form of connection with a radioreceiver detecting the low frequency audio waves carried and transmittedby the high frequency carrier Waves of the circuit as a pick-up from anantenna;

Fig. 3 is an elevation showing the different components of theequipment, including a talking picture projecting machine, sound adjunctto a radio and radio receiver adapted to be coupled, as shown in Fig. 1;and

Fig. 4 is a diagram showing a graph illustrating the result of the useof the circuit or wiring lo diagram as schematically shown in theligure.

Referring to the drawings, I designates a plug adapted to be connectedto an ordinary wall socket of the house wiring for supplying current,the same being connected by a lead wire 15 2 to a resistor 3 which maybe variable if desired. The respective electrical values of the elementsof this circuit are designated adjacent thereto, by way of example,especially in connection with the equipment designed for home 20 orlocal use and as explanatory thereof.

This resistor is connected to a contact 4 of a double pole double throwswitch 5, one terminal of the switch being connected 'by a lead 6to aconductor 'I and then through the heating iila- 25 ment of one or morerectier tubes. As shown, the lead is taken through the laments of tworectifier tubes 8 and 9 connected in series as shown and then to aresistor I0. Connectionis then made at II back to the switch 5 through30 a contact I2, constituting the other pole of the blade or knife ofthe switch opposite that from which lead 6 extends, and through aContact I3 opposing the contact 4, to a junction I4 to the iilament I5of an oscillator or oscillation unit 35 shown as a screen grid tube, itbeing understood that all o-f said tubes, heretofore referred to may beof any preferable type. Connection is then made in series to the heatingfilament of an amplifier tube, one or more of which can be used. Asshown, connection is made to nlaments I6 and I1 of two amplier tubes andthen through the lead I8 from the iilament I'I to the ground I9 and asuitable control switch 20 back to the source at the plug I. 45

The wire 22a. is connected to a contact 2| of the switch 5 opposite thecontact 4 with an interposed iilter choke 22 arranged and connected, aswill -be later described. The other contact 23 of the switch 5 oppositethe contact 2l is con- 50 nected to an interposed filter condenser 24applied to the circuit and operated when the blade of the switch 5 spansor engages the contacts 2l and 23.

An exciter lamp 25 is directly connected with 55 the resistance I8 andthe contact I2 on one side at the junction II and with the filament I5of the oscillator and contact I3 on the other side. This short circuitsthe eXciter lamp when switch 5 is in the heating circuit so that theexciter lamp will not burn out with the heating circuit surge. Thisexciter lamp is employed in connection with a condenser lense or lenssystem 26 through which the light from the exciter lamp passes and it inturn throws a very narrow beam of light on the sound film 21, that is, afilm with a sound track or sound on film which may be combined with apicture film. The sound lm is shown passing around the usual guide orgate, and window and a light sensitive cell or photoelectric tube 23.Light passes through the film 21 allowing the film to modulate thelight, and the modulated light falling on the photo-electric cell 28produces an alternating current exactly similar to the original sound onthe film. This is in turn impressed on the grid 29 of the amplifier tubenearest thereto, having the filament II, through a condenser resistornetwork A, the purpose of which is to compensate for any lack of low orhigh notes in the original recording. This network includes a resistance38 of suitable resistance to lower the overall gain Vto a desirablepoint connected to the photo-electric cell 28 with a series condenser 3|of such value as to pass all useful frequencies without attenuation, andhaving connected thereto in parallel, on the outside of the resistance38 and condenser 3I, a low-capacity condenser 32 of suitable value toreduce the reactance above a suitable reference frequency, decreasing inreactance the higher the frequency. This allows an increasing frequencycharacteristic for the high freouencies to the point where vthe gridcathode and plate cathode capacities prevent any further increase inhigh response. The low notes below a suitable reference frequency areadjusted by the increased reactance of a resistor capacity network Bincluding a medium capacity condenser 33 which is connected between thecondenser resistor network or unit A on one side. and `the grid 29,directly to the cathode 'I3 of the amplifier tube of the latter, with aninterposed resistance 34 as will be more fully described. The condenser33 is interposed between the resistance 34 and a resistance 35.Condenser 33 is in effect in parallel with the resistor 35, and aresistance 36 and a condenser 31 are interposed in the connection to thecathode '53. The rst va cuum tube ampli,- iier 38 having the filamentI'I and the control electrode or grid 29 is connected through its annodeplate 39 with a similar resistor network corresponding to condenserresistor .network A and the resistor network B or unit just described,Resistor network unit C includes a. condenser M. condenser` M.resistance 42. all in parallel with the circuit. Resistance 43, 43a. 44,and 44a and a condenser 4.5 are connected to the control electrode orgrid 45 of a second vacuum tube amplier 41 which latter is connectedwith the amplifier tube 38. The filaments IB and i'I constituting theheating elements thereof are connected in series. The current is thenpassed through a conventional resistor network D including a condenser48 and resistors 49, 58 and 5I of suitable resistance or reactance andas previously pointed out, all or any of which may be variable, ifdesired.

There is also a resistance 52, connected to the cathode of tube 4'Icorresponding to the cathode of the tube 38, corresponding to theresistance 3B, and another resistance 53 is connected to the cathode 55of an oscillator tube 54 constituting part of the oscillation unit Ewhich receives the amplified current from the tubes 38 and 4'I. Theoscillator tube 54 may be in the form of a heptode tube and has one grid55 thereof connected to the amplifier 4'I through the condenser 43, .Thegrid 5'I is connected through a variable condenser 58 with an inductance59 in parallel with an anode inductance 60 which is connected to theanode plate 6I of the oscillator tube 54 for the development of radiofrequency oscillations which are modulated by the previous amplifier andpicked up by a radio as designated at 62 or with an antenna 63 having aninterposed condenser 64 as a safety precaution. This antenna producesvibrations in the ether which can be received by a radio without directconnection thereto and spaced at a distance therefrom. The screen grid65 of the oscillator tube 54 is connected to the plate supply through aresistor 66 which is bypassed by a condenser 61 to ground 68. Theinductancev 59 having the variable condenser 58 connected thereto isalso connected to another resistance 69 and a condenser 'Ill connectedin parallel and in turn connected to ground I9.

The contacts 2| and 23 are connected through a condenser unit F with theground I8. The return wires of the circuits leading from the variousresistances are connected with another resistance 'II also connected toground through a condenser unit G interposed in the circuit includingthe amplifier tube 4'I while another condenser unit H is connected tothe amplifier tube 38. A resistance I2 is connected to the lead from thephoto-electric tube having connection with the control electrode or grid29 thereof and to the cathode T3 thereof with an interposed condenser 14and resistor capacity network or condenser unit B corresponding to theaforesaid condenser units including the elements 33, 34, 35, 35 and 31previously described. The cathode of the photo-electric cell orphoto-electric tube is thus directly connected to the cathode of thefrst amplifier tube instead of through a resistance and condensernetwork as used in connection with conventional circuits through ground.This has the advantage of reducing hum and increasing efficiency.Connection is also made through a resistance 15 with an adjustableresistance 'I6 on either side of the connection with the condenser unitH and a resistor TI from which connection is made through a resistor I8with ground '19.

Interposed in the circuit to the exciter lamp 25 is an adjustableresistance serving the purpose of a rheostat to vary the intensity ofthe lamp, thereby varying the signal volume.

While the talking picture projecting machine, including the case, filmcarrier reels, projecting lamp, lens and film gate, as Well as the soundmechanism heretofore described and adapted to be plugged into the housewiring at line voltage may be permanently associated together, they areshown as separate units in which the various wiring connections may becoupled at the plugs 8| and 82 through the medium of the coactingterminals 83, 84, 85, 86, 8'i, 88 and 89, which connect with the sockets83a, 84a, 85a, 86a, 81a, 88a, and 89a and which render the parts capableof physical as well as electrical disconnection. An ordinary radioreceiver is also illustrated at 62 as heretofore described, the samebeing preierably of the heterodyne type with a plurality of stages ofamplication, and including a plug 9U for connecting to the house wiring.However, as previously explained, instead of the physical connection ormutual indu-ctance permitting the elements to be plugged one into theother, the audio waves may be detected and picked up by means of theusual aerial or antenna fromthat of the signal reproducer andtransmitter to reproduce and transmit signals. While particularlyexplained in connection with audible signals or sound, it is to beunderstood that the principle is capable of application for all signalsand particularly those reproduced from an electrically recorded recordsuch as sound on film and adapted for any'electronic use.

Thus, in the operation of the circuit in the application of D. C. on thefilaments, starting at the plug I, electrical current flows along thelead 2 to the resistor 3. This resistor makes up the difference involtage between the D. C. output of the rectier tubes 8 and 9 and theline voltage. The current continues along into contact 4 and throughswitch 5 and lead 6 to I and from 'I through the filaments 8a and 9a ofthe rectifier tubes to the resistor I which reduces the voltage to therequired voltage of the balance of the tubesl and other load in thecircuit. Continuing to the point Il, the current from there is led backto the contact I2 of the switch 5 and through the contact i3, when theswitch is in the up or heating position, to the junction I4 leading tothe filament I5 of the screen grid tube or 0scillator Unit 54, tofilaments I6 and I1 directly through lead I8 to the ground I9 andthrough control switch 2li to the source or plug I connected to thehouse wiring or otherwise. This represents the starting procedure of oneembodiment of the application of the invention heretofore described.After reasonable time for the heating of the filaments 8a, 9a, I5, I6and I1, the switch 5 is thrown in the opposite or down position toengage the contacts 2| and 23, which is the D. C. position. The currentnow flows through the tubes of the filaments 8a and 9aappearing at I asa pulsating D. C. current and then iiowing through the switch 5 andcontact 2| and through the choke 22 to the various parts of the circuitas already described. The filter condenser 24 isI connected to thecontact 23 and, in the formy of the unit F is applied to the circuit tosmooth the D. C. pulsations appearing across the exciter lamp 25 andtube filaments.

The light from the exciter lamp 25 passes through the condenser lens orlens system 26 which in turn throws a very narrow beam of light on thesound film 2l. This' light passing through the film 2l allows the .filmto modulate the light and the modulated light falling on thephotoelectric cell 28 produces an alternating current exactly similar tothe original soundv on the film, and is impressed on the grid or controlelectrode 29 through the condenser resistor network A, the purpose ofwhich 'is to compensate for any lack of low or high notes in theoriginal recording which it does in this manner. The audio frequenciesare reduced to a certain proportion of their original amplitude by theresistance 30, condenser 3i being of such value as to pass all usefulfrequencies without attenuation. Condenser 32 is of suitable value toreduce the reactance above a suitable reference frequency, decreasing inreactance, the higher the frequency. This allows an increasing frequencycharacteristie for the high frequencies to the point Where the gridcathode and plate cathode capacities of the amplifier tubesy prevent anyfurther increase in high response. ble reference frequency are adjustedby the increasing reactance of the condenser 33 so that the effectivevalue of resistor 35 increases with the increasing reactance ciycondenser 33. The current is then amplified by the rst vacuum tube 38and is passed through a similar resistance network C corresponding tothe resistor network A, to the second vacuum tube II. The current ispassed through a conventional resistor network D to the oscillator tube54 in which the radio frequency is modulated. These radio frequencyoscillations may then be transmitted to the radio receiving set by anantenna or by a direct wire from the oscilla-tor to the radio set asalready described, or by the use of alternating or direct current lightpower supply lines.

From the foregoing, there will be observed that with the signalreproducing and transmitting circuits or a sound adjunct combined withsound on film or other electrically produced or recorded record such aslight produced vibrations, for radio receiving sets herein disclosed forreproducing and projecting or transmitting recorded audible or visualsignals or whereby signals or sound with or without pictures is producedand amplified for any electrical use, such as by means of a talkingpicture machine or a moving picture machine with sound on film or soundtrack nlm, in combination with or as an adjunct to a radio receiving setby direct connection thereto 4or by pick-up reproduction of thesignalseconomically without hum at the loud-speaker, with more amplincation andless light source, is possible. However, although the equipment isadapted for application to other methods of signal or sound recordationand reproduction, especially electrically as distinguished from purelymechanically produced records ysuch as a phonograph record, animportantffeature is the use of the equipment and circuit in connectionwith the sound track of a film or using the light passing through the lmto modulate the light falling on the photo-electric cell to produce analternating current corresponding to the original sound on the lm andthen amplifying and modulating radio frequency oscillations and themodulated output including the high frequency carrier waves and the lowfrequency audio waves which are picked up on the radio.

The normal circuit or circuits employed and the combination of arecorded signal transmitter circuit for reproducing signals particularlyby light or sound on film and the amplifying and rectifying circuitemployed whereby the equipment may be plugged into the ordinary linevoltage of the house wiring or otherwise on either direct cr alternatingcurrent and receiving such signals within the audible hearing range .0nan ordinary receiver preferably of the heterodyne type is of particularadvantage. By this means, the signals of the signal or sound reproducingcircuit will be received and amplified as well as economicallyreproduced in such a way as to eliminate the necessity for a highpowered audio amplifier and complicated and expensive equipmentordinarily required. Moreover, while one electronic use is shown, it isto be understood that the invention embraces the circuits andarrangements or combinations for other electrical uses where electricityor magnetic energy is used as an intermediary or means to effect suchreproduction or transmission of signals either audible or visual orboth. The apparatus will The low notes below a suitaf be simple,inexpensive and embodied in small units capable of being readilytransported or moved from place to place and constitutes animportantadjunct in a home or wherever it is desired to reproduce certain signalrecords as desired. Moreover, the signals will be free of hum, cracklingsounds or other interference and render possible the use of `moreamplification with less light source and current consumption.

Any suitable tone control means may be employed or inserted in thecircuit. In addition, by my circuits and arrangement or equipment, theequipment required for radio reception, and also as distinguished frompure audio amplification without radio reception, is reduced more thanone-half and the weight thereof is also reduced at least one-half.

It should be noted that the cathode of the photo cell 28 is connecteddirectly to the cathodes of the first amplifier tube. In Fig. 4 of thedrawings, a graph or diagrammatic illustration of the respectivecharacteristic curves of different control systems are shown. The curveA-A represents the characteristic curve of the present circuit for tonecompensation in which zero in decibels and 400 cycles per secondrepresent the desired mean ratios in the tone compensation between highand low frequencies or tones above or below a suitable referencefrequency which is the desired useful frequency and tone. It will beseen that both the low and high notes are so compensated for by the useof condenser resistor networks A and B, with each amplifying unit andparticularly in the first stage of amplification where a flow ofalternating current similar to the original sound record is produced,whereby each represents a gain in tone cornpensation and faithfulreproduction without attenuation and without undue attenuation in eitherhigh or low frequencies or tones beyond that of audible value. Thisgain, while represented so as to build up the lows and'the high, has theeffect of flattening or rendering more uniform the sound frequency curvetoward a constant value and to compensate for any lack of low or highnotes in the original recording so that the audio frequencies arerendered properly audible and tone quality improved. The curve B--Brepresents the characteristic curve of a resistance coupled amplifierwith tone control at minimum while the curve C-C represents thecharacteristic curve of a resistance coupled amplifier with tone controlat maximum and it will be noted from this that all desirable tonequalities are retained in my circuit, in properly amplified audible formso that the reproduction is greatly perfected, as shown by curve A-A.

In lieu of supplying D. C. to the filaments of the rectifier tubes, atransformer may be used to heat the filaments of the rectifier tubes tosupply direct current for the filaments of all other tubes or lampsused, where only A. C. is available but this is not nearly as desirableand is eliminated by the present circuit together with the hum and otherharmonic effects usually present from the employment of one or moretransformers.

While I have illustrated and described the preferred form ofconstruction for carrying my invention into effect, these are capable ofvariation and modification without departing from the spirit of theinvention. I, therefore, do not wish to be limited to the precisedetails of construction setI forth, but desire to avail myself of suchvariations and modifications as come within the scope of the appendedclaims.

I claim:

1. In signal reproducing means, a source of illumination, a. photo cell,a photographic record of sound, means to cause said record to travelbetween the source and the cell, a rectifier lncluding one or morerectifier tubes having filaments connected in series and through aresistance to the source of illumination for supplying the latter withcurrent at line voltage, a plurality of amplifying tubes havingfilaments connected in series, an oscillator tube having a filamentconnected in series therewith, condenser, resistor and filter means inthe circuit and a switch in the circuit adapted in one position tosupply A. C. or D. C. to the filaments until heated and in the otherposition to supply D. C. current to said tubes for energizing the wholecircuit.

2. In an electrical circuit for reproducing signals from an electricallyproduced sound record, a rectifier tube, a light source, an electricallyproduced sound record, a photo cell adapted to receive the light fromsaid source modulated by the record, one or more amplifier tubes havinga cathode directly connected to the cathode of the cell with interposedmeans to build up the low and high notes and render more uniform thesound frequency curve toward a constant value including resistorcondenser net works at least one of which is free of direct connectionwith thesupply line to the light source and cell and at least one ofwhich has direct connection with said line to the cell, means forreceiving the audio frequencies thus produced and to convert the sameinto radio frequencies for reception by a radio receiver and means forsupplying D C. to the filaments of all the tubes.

3. In signal reproducing means, an exciter lamp, a photo-electric tube,a photographic record of sound, means vto cause said record to travelbetween the source and the cell, a rectifier including one or morerectifier tubes having filaments connected in series and to the sourceof illumination, one or more amplifying tubes, an oscillator tube havinga filament connected in series therewith, a condenser, resistor andfilter means in the circuit, a switch in the circuit adapted in oneposition to supply A. C. to the filaments until heated and in the otherposition to supply D. C. current to said tubes for discharge as apulsating D. C. current and means to smooth the D. C. pulsationsappearing across the exciter lamp.

4. In signal reproducing means, an exciter lamp, a light sensitive tube,a photographic record of sound, means to cause said record to travelbetween the lamp and tube, a rectifier including one or more rectifiertubes having filaments connected in series for supplying the tube withcurrent, one or more amplifying tubes having filaments connected inseries, an oscillator tube having a filament connected in seriestherewith, condenser, resistor and filter means in the circuit and meansin the circuit to supply A, C. to the filaments until heated and then tosupply D. C. current to said tubes for energizing the whole circuit.

5. In signal reproducing means, a source of illumination, a photo cell,a photographic record of sound, means to cause said record to travelbetween the source and the cell, a rectifier including one or morerectifier tubes having filaments connected in series and through aresistance to the source of illumination for supplying the latter withcurrent at line voltage, a plurality of amplifying tubes having lamentsconnected in series, an oscillator tube having a filament connected inseries therewith, condenser, resistor and filter means in the circuitand means in the circuit adapted in one position to supply A. C. or D.C. to the filaments until heated and in the other position to supply D.C. current to said tubes for energizing the whole circuit.

6. In signal reproducing means, a source of illumination, aphoto-electric cell, an electrically produced record of sound, means tocause said record to travel between the source and the cell, a rectifierincluding one or more rectifier tubes having laments connected in seriesand through a. resistance to the source of illumination for supplyingthe latter with current, an oscillator, a resistance in the circuitbetween the oscillator and source of illumination, a plurality ofamplifying tubes connected in series with the oscillator and means toautomatically compensate for any lack of high or low notes in theoriginal recording with an increasing frequency characteristic for thehigh notes and automatic adjustment of the low notes below a suitablereference frequency free of transformers and manual control, including acondenser resistor network having a low capacity condenser ccnnectedthereto in parallel on the outside and an additional resistor condensernetwork in the circuit on the outside of the first condenser andresistance to prevent any further increase in high response and toadjust the low notes below a suitable reference frequency by increasingreactance of one of said condensers so that the effective value of theresistor increases with the in-creasing reactance thereof.

7. A signal reproducing means including a signal record eiected bylight, means including a light sensitive cell to produce a pulsatingcurrent corresponding to the original record by passing light throughthe record and modulating the same for action on said pulsating currentproducing means, a condenser resistor network having a series condenserconnected with the light sensitive cell, a low capacity condenserconnected to the cell in parallel on the outside of the resistance andcondenser of suitable value to automatically compensate for any lack ofhigh or low notes in the original recording and reduce theaudio-frequencies at or above a suitable reference frequency to acertain proportion of their original amplitude and to amplify normallyattenuated low and high notes which are indistinct to a greater degreethan the reference frequency so that the notes that are imperfect in theoriginal recording toward a mean ratio and reference frequency betweenhigh and low frequencies are compensated for and means for amplityingand converting such frequencies with a gain in both high and low notesto render thel same capable of detection and reception by a radioreceiver.

8. A sound motion picture projector comprising a motion picture filmbearing a sound tract, optical means to project the motion pictures fromsaid nlm and means for reproducing sound from said sound tract includinga source of light to illuminate said sound track, a source of directcurrent to supply said source of light including one or more rectifiertubes to receive A. C. current at line voltage, and an adjustableresistance between the rectifier tubes and the source of light, aphoto-electric cell adapted to receive light modulated by said soundtrack, one or more amplier tubes having a cathode directly connected tothe cathode of the photo-electric cell, means interposed to build up thelow and high notes and render more uniform the sound frequency curvetoward a constant value and to automatically compensate for lack of bothhigh and low notes including a resistor condenser network and means forreceiving the audiofrequencies thus produced and to convert the sameinto radio frequencies.

WALTER C. WELLMAN.

